1. Field
The present invention relates generally to radiation detection systems and in particular to enhanced resolution radiation detection.
2. Description of the Related Art
Detection of radiation that is emitted from objects and is outside of the visible spectrum can provide useful information. For example, detection systems have been developed for sensing infrared radiation (IR) from an object or source in a target space. Infrared imagers, also called thermal imagers, are instruments that create images of heat instead of light, by converting radiated IR energy to a corresponding map of temperatures or radiance. IR sensing applications including temperature measurement and mapping, forest fire sensing and suppression, and surveillance.
Thermal imaging systems are generally constructed from a variety of different types of infrared detectors. Infrared detectors can be classified as cooled or uncooled. Uncooled detectors include thermal sensors that generate a change in a physical parameter of the detector, such as resistance, due to a change in detector temperature resulting from incident infrared radiation. Cooled detectors include infrared sensors where the change in the physical parameter of the sensor is due to a photoelectron interaction within the material of the sensor.
To detect thermal variation across a target space, thermal imaging systems often use two-dimensional arrays of infrared detectors. In a typical thermal imaging system, the radiation from a target space object will be focused onto a detector array. Electronic or mechanical scanners are generally employed to measure the radiation detected by each detector in the array and thereby produce a two-dimensional display corresponding to a thermal map of the object being imaged. The size and active area of each sensor in the array limits the spatial resolution of the imaging system. Likewise, the need to make electrical connection to the individual detectors, for example to measure a resistance change, can increase system complexity as well as impose constraints on the minimum size for the detectors.
Liquid crystal materials can change color in response to received thermal energy. Typically, liquid crystal materials are used for indicating thermal change and are supplied in film form, or as a coating. In a typical application, a liquid crystal film or coating may be applied to a radiating surface of an object for direct sensing of surface temperature by observing variations in color across the liquid crystal material as a result of the object's surface temperature profile.
Because liquid crystal films are not made up of individual detectors, they do not have the drawback of being limited by a minimum detector size. Also, because liquid crystal films are directly viewed, there is not the need for electrical connections to detect changes in physical parameters. However, liquid crystal films suffer from poor resolution because the thermal energy “bleeds” across the film or coating.
Thus, a need exists for improved methods and apparatus for the detection of radiation emitted from objects. Other problems with the prior art not described above can also be overcome using the teachings of the present invention, as would be readily apparent to one of ordinary skill in the art after reading this disclosure.